Discussion

Abstract

Previous architectonic studies of the medial geniculate body based on Nisslor fiber-stained material in marsupial species have reported subdivisions different than those in the present investigation (Figs. 2–4; see also Winer etal. 1987). Several observers have subdivided the opossum medial geniculate body into a central nucleus and an outer shell, or marginal nucleus (Chu 1932 a; Loo 1937; Bodian 1939; Oswaldo-Cruz and Rocha-Miranda 1967). In other marsupials, such as the brush-tailed possum (Trichosurus vulpecula), comparable, broad divisions into principal and internal nuclei have been drawn (Haight and Neylon 1978 a), and a similar analysis has been made for the hedgehog (Talpa europaea) medial geniculate body (Ebbesson etal. 1972). Although the cytoarchitecture of these species bears a superficial resemblance to the opossum medial geniculate body, no inferences of presumptive homology can be drawn without more detailed investigation, nor can the results of these studies be readily compared with the present findings.